DESCRIPTION: The investigators have now cloned the cDNA encoding a homeobox transcription factor related to Drosophila NK2. As the seventh vertebrae factor in this family, the new factor is tentatively designated PCF/Nkx2.7. Nkx 2.1 to 2.6 are all developmental regulators of organogenesis, and studies are proposed to determine the role of PCF/Nkx 2.7 in liver development and neoplasia. Aim 1 studies will focus on the new gene: the transcriptional regulatory controls will be characterized, and in addition, a closely related gene will be cloned and sequenced. In Aim 2, the properties of the PCF/Nkx 2.7 molecule will be analyzed by deletion of peptide domains and GAL4 gene fusion. Subsequently, the binding partners will be determined using direct assays and the yeast two-hybrid system. Aim 3 evaluates the role of PCF/Nk 2.7 in development through analysis of embryos and cell cultures. A mouse inducible gene targeting model will be used to confine gene knock-out to the foregut, the embryonic region that gives rise to the liver, or to the early embryo. Finally, Aim 4 deals with cancer -related aspects. A rearranged PCF/Nkx 2.7 has been found in a human hepatocarcinoma cell line, suggested a possible role in cell transformation. This putative translocation will be sequenced and mapped. Studies will evaluate PCF/Nkx 2.7 as a transforming gene in cell lines, and in primary culture of hepatocytes. Together these Aims represent a comprehensive approach to this new gene, based on the model that abnormal reactivation of PCF/Nkx 2.7 recapitulates developmental controls to transform liver cells.